This is ISPF stats. Been around since the 1970s and SPF version 1. Version (VV) is sort of arbitrary. Starts at 1 and can be changed via 3.5. Mod (MM) updates with each use of the member; basically means nothing useful. MOD as in lines modified (or something like that) also seems - to me -- to be meaningless and useless. Several years ago I wrote a line mode command to list PDS members.

Notice I didn't format MOD, mostly because I wanted this to fit on a line and the extra 8 bytes (a blank and 7 digits to support extended stats) was too much. Partly it's related to my style. I don't use PDS for development because of the data management issues. Lots of saves, and all of us know what that means for data management. If I'm going to fiddle with ADDSTATS, for example, I copy it to sequential and update the sequential data set. When I'm done I delete the PDS member and start a new member by copying the sequential data set to the PDS.

AFAIR the field MOD is maintained by ISPF only when member lines are numbered in standard manner?

First RENUM command fills all positions 73-80 with 'NNNN0001' where '0001' stands for "change counter", and increased by 1 after any change of every single line. Looks like MOD value is produced as sum of all 4-digit change counters of all lines. So, after some lines are deleted, the MOD value decreases in accordance with this sum!

I'm lazy to verify this. Agree that nowadays it is meaningless, and useless.

VV.MM
Version number and modification level. The version number is set to 1 and
the modification level is set to 0 when the member is created. The
modification level is the number of times this version has been modified.
For example, 02.15 means version 2, modification 15.
If a member name is just an alternate name for another member, ALIAS
appears in this field.

The VV changes when you (or someone working at your site) goes into the appropriate ISPF screen and manually updates the VV. It otherwise stays at 01 as the quote indicates.

AFAIR the field MOD is maintained by ISPF only when member lines are numbered in standard manner?

First RENUM command fills all positions 73-80 with 'NNNN0001' where '0001' stands for "change counter", and increased by 1 after any change of every single line. Looks like MOD value is produced as sum of all 4-digit change counters of all lines. So, after some lines are deleted, the MOD value decreases in accordance with this sum!

I'm lazy to verify this. Agree that nowadays it is meaningless, and useless.

No. mm increases by 1 each time the member is edited. ISPF never reduces mm on its own.

ISPF member statistics are totally useless, and every one of them can be set to whatever values you want them to be set to via the LMMSTATS function. I have text members with a creation date of 1978, (seven years before I started as a programmer) and PL/I source with a creation date of 2099-12-31. And about half my members have a userid that doesn't even exist on the systems I'm working on.

ISPF member statistics are totally useless, and every one of them can be set to whatever values you want them to be set to via the LMMSTATS function. I have text members with a creation date of 1978, (seven years before I started as a programmer) and PL/I source with a creation date of 2099-12-31. And about half my members have a userid that doesn't even exist on the systems I'm working on.

True. As Prino says, it is all to easy to subvert them. VV MM and user can easily be altered via 3.5, and a half way intelligent programmer can subvert the remainder through a program.

ISPF member statistics are totally useless, and every one of them can be set to whatever values you want them to be set to via the LMMSTATS function. I have text members with a creation date of 1978, (seven years before I started as a programmer) and PL/I source with a creation date of 2099-12-31. And about half my members have a userid that doesn't even exist on the systems I'm working on.

True. As Prino says, it is all to easy to subvert them. VV MM and user can easily be altered via 3.5, and a half way intelligent programmer can subvert the remainder through a program.

It is important to remember that member statistics are not a part of the z/OS file system. Member stats are stored in the so-called "user area" of a PDS directory. As the name implies, the contents and usage of the "user area" is up to the user of the data set, in this case ISPF. Other programs that update PDSes may use the "user area" for other purposes.

As Mark Twain might have said: "There are lies, damned lies, and member list statistics".